1. Background Field
The present application is directed to location determination in short range wireless networks and more particularly to establishing static node positions in a short range wireless network using existing protocol mechanisms not related to location.
2. Relevant Background
With the ever-increasing demand for wireless solutions to common short and medium-distance connection problems, ad-hoc wireless networks under, for example, wireless personal area network (WPAN) standards, such as the IEEE 802.15.4-2003 standard, have been gaining popularity. Examples of such network standards include WiFi and Bluetooth®. However, there is room for expansion of capabilities in existing WPAN standards. For example, existing WPAN standards such as Bluetooth® have established wake up latencies in the order of seconds leading to relatively higher power consumption over time. New lower power standards have since emerged, such as the ZigBee standard. ZigBee is a standard for a communication protocol using small, low-power short range digital radios to facilitate connections between such devices as wireless headphones and cell phones. It should be noted that the term ZigBee is used throughout the document and, for convenience the trademark symbol is omitted, however ZigBee is a registered trademark belonging to the ZigBee Alliance. The technology defined by the ZigBee specification is intended to be simpler and less expensive and targeted at applications that require a low data rate, long battery life, and secure networking. Wake-up latencies under the ZigBee standard are on the order of milliseconds, leading to large power savings. However, the ZigBee standard is still emerging and does not define a mechanism for positioning of nodes.
It is well appreciated that positioning information can be important. For example in the case of an alarm or failure notification from a static node associated with critical equipment, positioning information is crucial for dispatching repair or other appropriate services. Further, the positioning of mobile nodes within a network, such as within certain zones, can become important for security purposes and other related purposes such as tracking the movement of mobile nodes within the area served by the network.
In accordance with the conventional art, the static node positioning issue is currently resolved at the application layer through the use of proprietary messages and applications. Thus, mobile nodes configured for operation in accordance with the standard protocol can not conform to the proprietary location services without the proprietary application. Further, in such proprietary networks, zone tracking is accomplished using excessive amounts of overhead. In some tracking and security applications, the behavior of an object under control depends on the zone location. For example, when a child, who is being tracked through the use of a short-range wireless device, enters a school region during a school day a safe state is assigned to the child based on the detected location as being within the school region. When the child leaves the school region during a school day an unsafe or alarm state can be generated. In order to accomplish such tracking, in accordance with conventional techniques, a zone under control, such as a school, may be bounded by an RF fence made up of a number of static nodes deployed along the physical boundaries of the desired fence. The static nodes can be set in internal spaces such as classrooms so that the whole zone is covered by one or more bounded networks using special applications such as home control, energy saving, or the like. The special applications can run on zone controllers or zone routers and listen to activity of any ZED that are currently in the network and pass collected information such as RSSIs to ZC where the MZED location is calculated upon the supplied information. The above described method requires proprietary applications on the static nodes and wastes limited ZigBee RF resources.
It would be desirable in the art to use existing protocol mechanisms for generating positioning information. Such an approach would avoid excessive consumption of wireless resources, both on the static nodes and on zone controllers and routers.